Remember league of black cleaver?

The stacking is the important part though. That's like saying Ebola was as bad as the Black Plague, even though Ebola only killed 10-15 000 people and the Black plague 75-200 million people. Both were terrible diseases that killed a ton of people, but one was clearly worse. Duskblade is being built on a lot of ADs, but it's nowhere as bad as when nearly every single champion built 5-6 cleavers. Both were (are) exceptionally strong items, but one was in a league on its own.

The mage rework was almost secondary in it's own patch. Most of the changes to champions were basically inconsequential (vel, brand, zyra), the hextech items are sitting at around a 4% sum purchase rate (including gunblade) and the majority of the patch's resources went into dividing support and mage itemization and the introduction of elemental dragons, rather than quality of life changes and compelling uniques.

Yes mages got their own update. The largest class, excluding fighters (but juggernauts had already gotten theirs), was pushed into a single update and even then, they were given significantly less consideration in their own update than any other class update. As the only other class update which implemented or changed core game mechanics was the tank update, but that was an update to rift hareld which was, and still is, a less core and influential mechanic than dragons.

Oh, and i almost forgot. They outright removed spell vamp and WotA with it.